Data storage devices, for example a product of the EMC, VNX2, provide a disaster recovering system of the file level. If a disaster occurs on a primary storage device, the selected network attached storage (NAS) server, together with all its file systems, snapshots, and network configurations, can be switched to a secondary storage device through a continuous data service.
However, there might be a case that the primary storage device may be interrupted due to outage. After the primary storage device is recovered from an interruption state, the data on the secondary storage device cannot be automatically replicated to the primary storage device. As an example of the disaster recovery, VNX2 provides a disaster recovery service of the file level by using a MirrorView/S solution. In the solution, a mirrored pair is created for a pair of logical units (LUNs). The LUN of the primary storage device serves as a primary mirror in the mirrored pair, and the LUN of the secondary storage device serves as a secondary mirror in the mirrored pair. The mirrored pair is placed in a consistency group and managed collectively as a single entity.
When the primary storage device does not respond normally or is interrupted during switchover, the single consistency group is destroyed, resulting in two local consistency groups. Hence, when the primary storage device is recovered from the interruption state, the data on the secondary storage device cannot be automatically replicated to the primary storage device through the two local consistency groups. In other words, the data replication is interrupted.
In the case of the two local consistency groups, although the NAS client may continue to access the data on'the secondary storage system, the altered/updated data cannot be replicated to the primary storage system. This would cause the data to be unprotected. A user may try to re-create the mirrored pair and the consistency group, but it is difficult to find the corresponding primary mirror and secondary mirror.